Compensated flyweight



3,181,372 Patented May 4, 1%65 3,181,372 Cflh IPENSATED FLYWEIGHTPaulmer D. Hunt and James R. Goerke, South Bend, Ind, assignors to TheBendix Corporation, a corporation of Delaware Filed Sept. 29, 1953, Ser.No. 763,887 13 Claims. (Cl. 73-497) The present invention relates tocentrifugal weight members and more particularly to centrifugal weightmembers to be rotated in a fluid medium.

It is often necessary when utilizing centrifugal weight members, torotate said flyweights in a fluid medium. For example, in the gasturbine engine fuel control art, flyweights are commonly included aspart of a fluid immersed governor apparatus as illustrated in US.Patents 2,644,513, F C. Mock, issued July 7, 1953; and 2,7 05,047, H. J.Williams et al., issued March 29, 1955 (common assignee). In suchapplications the rotating action of the flyweights cause a rotation offluid resulting in a pressure gradient in the surrounding fluid thatincreases with the distance from the spin axis of the governormechanism. This fluid pressure gradient acts over the surface of therotating centrifugal Weights producing an undesirable force acting onthe flyweights. The force is particularly undesirable because it dependson the density of the fluid medium, which in turn changes withtemperature, and is different for various fluids such as fuel, oil, orthe like.

Accordingly, it is an object of the present invention to provide acentrifugal weight member adaptable for operation in a fluid medium andinsensitive to changes in fuel due to variations of temperature or type.

It is another object of the present invention to provide a centrifugalWeight member having a counter weight of different density to eliminatevariations due to density change of the fluid in which said centrifugalweight is operating.

Other objects and advantages of the present invention will becomeapparent from the following description and accompanying drawingswherein:

FIGURE 1 is a cross sectional view of a fluid immersed governorapparatus having a centrifugal Weights in accordance with the presentinvention, and

FIGURE 2 shows the novel centrifugal weights of the present inventiondisassociated from the remaining governor apparatus.

Referring to FIGURE 1, a housing 12 having a fluid inlet conduit 14 anda fluid outlet conduit 16 forms a fluid containing chamber and governorhousing. A plurality of centrifugal weight members 18 are containedwithin housing 12 and pivotably secured to brackets 26 at pinnedconnection 22. Said brackets are in turn secured to a rotatable spintable 24 at a spaced distance from its axis of rotation. The centrifugalweight members 18 are each comprised of a flyoall element 26, acounterweight element 28, and a lever or foot member 30. A rotatableinput shaft 32 is secured to spin table 24 and extends externallythrough housing 12 where it is connected to a gear 34 which is adaptableto receive a rotating input, such as an engine speed or the like. Anaxially movable shaft 36 includes a diametrically enlarged portion 33 onone end which contacts foot member 38; said shaft extends throughhousing 12 where a pilot valve 4% is formed on its opposite end. Pilotvalve 4%) is operative with a supply of control fluid in conduit 42 tocontrol the position of piston 44 in a manner well known to thoseskilled in servo control art. Piston 44 includes a first axially movablerod 46 operative to control thc speed of an engine, not shown, as bycontrolling the position of an accelerator, throttle lever, valve or thelike. A sec- 0nd axially movable rod 48 is positioned by movement ofpiston 44 and extends into housing 12 where it positions movableretainer 50 and spring 52 to provide a feedback balancing force tomember 38 that is responsive to the position of piston 44.

Certain of the novel design features of centrifugal weight 13 can bemore clearly described by an analytical analysis of the forces acting onsaid weight. Accordingly, the significant forces acting on centrifugalweight 18 are illustrated in FIGURE 2, where:

F represents the centrifugal forces generated by the rotary motion andacting radially outward at the respective centroids of flyball element26 and counterweight 28;

F represents the net forces due to fluid pressure acting on centrifugalweight 18 acting radially inward at the centroid of the respectiveweight elements; and

F represents the reaction force acting on foot element 30, which forms amoment equal and opposite in direction to the output moment produced bycentrifugal weight 18. The axis of rotation and a line perpendicularthereto passing through pivotable point 22 form a pair of coordinatereference lines for the following analytical analysis.

Centrifugal force F may be expressed as:

( F Mr where the symbols have the following meaning:

M=spinning mass r =radial distance of centroid of mass to axis ofrotation 0=angular velocity The following relationships are also wellknown:

( M=dV 6=(constant) N where d is density of the mass and V its volume,and N is rotating speed in r.p.m.

Substituting Equations 2 and 3 in Equation 1 gives:

( F: KN dVr as set forth in the text Elementary Mechanics of Fluids, byH. Rouse, page 69, and where j is fluid density. The equation may beexpressed in terms of force acting over a particular area within saidcylinder as:

where A is the area of an object over which the pressure acts.

Turning to FIGURE 2, the fluid pressure force F acting on fiyballelement 26 and counterweight 28 is the difference between the fluidpressure force acting over the inwardly extending surface and the forceacting over the outwardly extending surface and may be expressed:

but since the radially inward projected area of an object equals itsradially outward projected area, A and A are the same and may becharacterized by the single symbol A. Then:

factoring the radical:

I then the equation reduces to:

and y be equated, but-only their product.

, counterweight.

. r 3 and since r r is the width (W) of the weight elements and r +requals '2r Equation 9 maybe expressed:

It should be noted, that there is substantial similarity betweenEquations 4 and 1 2 so that for purposes of clarity all symbolsspecifically referring to flyball element 26 will be identified withsubscript 1 and symbols referring The output force F may be expressed interms of other forces by taking the sum of the moments about pivotableThen regardless of the change in fuel density j the output force F isconstant at design speed N. .Thus the object' of the invention toachieve acentrifugal weight for rotat ing in a fluid medium that issensitive to density changes of the fluid in'which it 'is rotating isattained.- It should be noted, that it is not necessary that theseparate characteristics of the flyball 26 and counterweight 28 of V, r7 Thus, for example, it is-not necessary that the volume of both said.flyball and said counterweight be the same but only the product ofvolume times the dimensions r and y.

The present invention has been described by use of precise mathematioa-lformulae to illustrate more clearly the object and function of thepresent invention. The formulae used, however, should not be construedas'an unnecessary limitation on the scope of the present invention whichin its broad analysis disclosed the idea of reducing the effect of fluiddensity changes on centrifugal Weights spinning in a fluid medium by theaddition of a Failure to satisfy the precise mathematical formulaeshould be considered a departure in degree only and not an avoidance ofthe fundamental novel'idea disclosed herein.

We claim:

1', v A centrifugal weight having an axis of rotation and a pivotablepoint located a spaced distance from said axis of rotation comprising:first and second interconnected masses located on opposite sides of aplane passing through said pivotable point and perpendicular "to theaxis of rotation; said first mass composed of material having a greateraverage'density than said second mass; and the products of the volume,the distance from the I centroid to the axis of rotation, andthexdistance from the centroid to said plane of said first and secondmasses are equal.

2. A centrifugal weight forrotation in a fluid medium having an axis ofrotation and a' pivot point located a spaced distance from said axis ofrotation comprising: a flyweight rnember movable about saidpivot pointand to counterweight 28 will bear subscript 2.

operative to produce a' centrifugal force that varies as a function ofthe rate of rotation about said axis of rotation, said flyweight membersubject to an unwanted force due to a pressure gradient in the fluidmedium in which said flyweight is rotating, said fluid medium subject todensity variations operative to vary the magnitude of said unwantedforce and introduce a force error responsive to changes in fluiddensity, counterweight means movable about said pivot point forreceiving a counteracting force due to said pressure gradient which isoperative to nullify said unwanted force and said force error responsiveto changes in fluid density, said' counterweight having a density lessthan said flyweight so that centrifugal force is not nullified.

3; Ina fluid immersed governor, the combination of a revolving support,centrifugally and diflerentially acting weights arranged in pairscomprised of a flyweightand a counterweight, a lever for interconnectingsaid flyweight and said counterweight, a bracket mounted on saidsupport, a pivot for said lever situated between said flyweight and saidcounterweight and supported by said bracket, said counterweight composedof material having less average density than said fiyweight, and a meanswhich opposes the resultant action of the weights.

4. In a fluid immersed governor, the combination as claimed in claim 3wherein flyweight and said counterweight have substantially the samevolume.

5. In a fluid immersed governor, the combination claimed in claim 4wherein the distance of the flyweight centroid from said pivot issubstantially the same as the distance from the counterweight centroidto said pivot.

6. In a fluid immersed governor, the combination of a revolving support,centrifugally and differentially acting weights arranged in pairscomprised of a flyweight and a counterweight, a leverfor'interconnecting said flyweight and said counterweight, a bracketmounted-on said support, a pivot for said lever situated between saidflyweight mounted to rotate about the axis at a distance equalto a fluidmedium, said device comprising a body adapted the first radius; anoutput member; and means connecting said first and second flyweights tosaid output member to exert opposing forces on said outputtmember, themechanical advantage of the means being the same for both fly- Weights.

8. A speed responsive device adapted to operate within to be rotated inaccordancewith a parameter of speed, mounting members operativelyconnected to said body and adapted to be rotated with said body, pivotmeans retained by said mounting members, centrifugally responsiveflyweight members including a main body portion mounted on said pivotmeans adapted in passing through said fluid medium t'ovcreate acentrifugal force which is a function of the speed of rotation of saidbody, said main body portion having an inner surface relatively closerto the center of gyration of said flyweight member and an outer sur facerelatively farther away from the center of gyration of said flyweight,said inner and outer surfaces'being effective for creating a firstcentrifugal pumping force opposing the centirfugal force created by thespeed of rotation of'said flyweights, and a second body portion securedto said flyweight so as to be normally urged by centrifugal 7 posite tothe direction of travel incurred by said main body force in a directionof travel about said pivot means opportion due to its centrifugal forceand having a second inner surface and a second outer surface thereon,said second inner surface and said second outer surface being of suchareas as to cause a second centrifugal pumping force of a magnitudesubstantially equal to and in opposi-r ticn to said first centrifugalpumping force.

9. A flyweight governor having a first flywe'ight and a second tlyweightdisposed to rotate about an axis, a movable member, first and secondconnecting means connected, respectively, from said first fiyweight tosaid member and from said second fiyweight to said member to impartopposing forces to said member, the magnitude of 1 said forces beingdependent upon the speed of rotation,

the density of said fiyweights being unequal, and the prodnot of thequantities comprising volumertric displacement, mechanical advantage ofthe associated connecting means, and radius of gyration of said firstfiyweight being substantially equal to the product of the likequantities of said second fiyweight so that the resultant of saidopposing forces on said movable member is constant regardless of thedensity of the medium surrounding said flyweights.

10. In a fiyweight governor for operation in a fluid medium of variabledensity, a first flyweight and a second fiyweight disposed to rotateabout an axis and to produce centrifugal forces thereby, output meansresponsive to force, connecting means connecting said first fiyweightand said second flyweight to said output means to apply said forces inopposing relation tmreto, the density of said fiyweights being unequal,and the product of the quantities comprising volumetric displacement,mechanical advantage of the associated connecting means, and radius ofgyration of said first fiyweight being substantially equal to theproduct of the like quantities of said second flyweight so that theresultant of said opposing forces is independent of the density of themedium surrounding said flyweights.

11. In a flyv/eight governor for operation in a fluid medium of variabledensity, a first fiyweight and a second flyweight of unequal densitydisposed to rotate about an axis and to produce centrifugal forcesthereby, output means responsive to force, connecting means connectingsaid first fiyweight and said second fiyweight to said output means toapply said forces in opposing relation thereto, the product of themechanical advantag the radius of gyration, and the volume of said firstfiyweight being equal to like quantities of said second flyweight, andmeans for maintaining the radii of gyration of said fly- Weightssubstantially constant throughout the operating range of the governor.

12. A fiyweight governor comprising: a first flyweight and a secondflyweight of different densities disposed to rotate about an axis;output means responsive to force; connecting means arranged to causesaid flyweights to impart force from said fiyweights to said outputmeans so that said output means produces an output that varies with thedifference between forces due to said first and said second fiyweights;the characteristics of said first and second fiyweights, said connectingmeans, and said output means being such that variations in the densityof the medium surrounding said fiyweights have substantially no elfecton said output according to the relation:

o= 1"1 1( 1-j) 2 '2 2( z"i) wherein,

F is the resultant of the forces imparted to said member, Y is themechanical advantage of the means connecting said first set offiyvveights to said member, r is the radius of gyration of said firstset of flyweights, 6 is the angular velocity of said flyweights, V isthe volume of said first set of fiyweights, Y is the mechanicaladvantage of the means connecting said second set of fiyweights to saidmember, r is the radius of gyration of said second set of hyweights, Vis the volume of said second set of fiyweights, al is the density ofsaid first set of fiyweights, d is the density of said second set offlyweights, j is the density of said fluid medium, and Y1l2 V2: Yzrg V2and means for maintaing the radii of gyration of said fiyweightssubstantially constant over the range of operation of the governor.

13. Apparatus of the class described comprising, in combination: a firstflyweight having an effective density d a volume V and mounted forrotation about an axis at a radius r an output member; means connectingsaid first flyweight to transmit a first force to said output memher,said means providing a mechanical advantage Y be tween said firstflyweight and said output member; a second fiyweight having an effectivedensity 42 a volume V and mounted for rotation about an axis at a radiusr and means connecting said second flyweight to transmit a second forceto said output member in a direction opposite the first force, the lastnamed means providing a mechanical advantage Y between said secondfiyweight and said output member, the relationship between the volumes,radii and mechanical advantages being 1 1 1= z a z and the effectivedensity d, being different than the effective density d References Citedby the Examiner UNITED STATES PATENTS 742,874 11/03 Junggren 264-152,627,906 2/53 Johnson 26415 RICHARD C. QUEISSER, Primary Examiner.

s. LEVINE, JAMES J. GILL, JOSEPH P. STRIZAK,

Ex i s

3. IN A FLUID IMMERSED GOVERNOR, THE COMBINATION OF A REVOLVING SUPPORT,CENTRIFUGALLY AND DIFFERENTIALLY ACTING WEIGHTS ARRANGED IN PAIRSCOMPRISED OF A FLYWEIGHT AND A COUNTERWEIGHT, A LEVER FORINTERCONNECTING SAID FLYWEIGHT AND SAID COUNTERWEIGHT, A BRACKET MOUNTEDON SAID SUPPORT, A PIVOT FOR SAID LEVER SITUATED BETWEEN SAID FLYWEIGHTAND SAID COUNTERWEIGHT AND SUPPORTED BY SAID BRACKET, SAID COUNTERWEIGHTCOMPOSED OF MATERIAL HAVING LESS AVERAGE DENSITY THAN SAID FLYWEIGHT,AND A MEANS WHICH OPPOSES THE RESULTANT ACTION OF THE WEIGHTS.